You could using several binary rate multiplier in series such as the CD4089
Specialty Logic - Rate Multipliers/Frequency Dividers/Timers - CD4089B - TI.com. These allow you to do fractional multiplying of a digital input frequency. Each chip allows multiplication of the input frequency by 1/16 to 15/16.
By cascading them you can get arbitrarily close to your desired divide ratio (to be within the accuracy of your speedometer). For example, if you cascade two chips in the "Add" mode with the first multiply ratio of 5/16 (80/256) and the second multiply ratio of 13/256, the total multiply ratio will be 93/256 for a divide ratio of 256 ÷ 93 = 2.752, which is within 0.3% of the desired value.
For even higher accuracy you could cascade more chips.